From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C8C1BC433DF for ; Thu, 20 Aug 2020 12:59:01 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A4AAE20674 for ; Thu, 20 Aug 2020 12:59:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A4AAE20674 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 84EE91353AD99; Thu, 20 Aug 2020 05:59:00 -0700 (PDT) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=195.135.220.15; helo=mx2.suse.de; envelope-from=jack@suse.cz; receiver= Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 3CFEC134BE035 for ; Thu, 20 Aug 2020 05:58:57 -0700 (PDT) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 80BA9AC7D; Thu, 20 Aug 2020 12:59:23 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E41321E1312; Thu, 20 Aug 2020 14:58:55 +0200 (CEST) Date: Thu, 20 Aug 2020 14:58:55 +0200 From: Jan Kara To: Vivek Goyal Subject: Re: [PATCH v3 02/18] dax: Create a range version of dax_layout_busy_page() Message-ID: <20200820125855.GL1902@quack2.suse.cz> References: <20200819221956.845195-1-vgoyal@redhat.com> <20200819221956.845195-3-vgoyal@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200819221956.845195-3-vgoyal@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Message-ID-Hash: 3AK3TH73IRQGCTFTYL7QUX52CTBXIHIC X-Message-ID-Hash: 3AK3TH73IRQGCTFTYL7QUX52CTBXIHIC X-MailFrom: jack@suse.cz X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, virtio-fs@redhat.com, miklos@szeredi.hu, stefanha@redhat.com, dgilbert@redhat.com, Jan Kara X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Wed 19-08-20 18:19:40, Vivek Goyal wrote: > virtiofs device has a range of memory which is mapped into file inodes > using dax. This memory is mapped in qemu on host and maps different > sections of real file on host. Size of this memory is limited > (determined by administrator) and depending on filesystem size, we will > soon reach a situation where all the memory is in use and we need to > reclaim some. > > As part of reclaim process, we will need to make sure that there are > no active references to pages (taken by get_user_pages()) on the memory > range we are trying to reclaim. I am planning to use > dax_layout_busy_page() for this. But in current form this is per inode > and scans through all the pages of the inode. > > We want to reclaim only a portion of memory (say 2MB page). So we want > to make sure that only that 2MB range of pages do not have any > references (and don't want to unmap all the pages of inode). > > Hence, create a range version of this function named > dax_layout_busy_page_range() which can be used to pass a range which > needs to be unmapped. > > Cc: Dan Williams > Cc: linux-nvdimm@lists.01.org > Cc: Jan Kara > Cc: Vishal L Verma > Cc: "Weiny, Ira" > Signed-off-by: Vivek Goyal > --- > fs/dax.c | 29 +++++++++++++++++++++++------ > include/linux/dax.h | 6 ++++++ > 2 files changed, 29 insertions(+), 6 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index 95341af1a966..ddd705251d9f 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -559,7 +559,7 @@ static void *grab_mapping_entry(struct xa_state *xas, > } > > /** > - * dax_layout_busy_page - find first pinned page in @mapping > + * dax_layout_busy_page_range - find first pinned page in @mapping > * @mapping: address space to scan for a page with ref count > 1 Please document additional function arguments in the kernel-doc comment. Otherwise the patch looks good so feel free to add: Reviewed-by: Jan Kara after fixing this nit. Honza > * > * DAX requires ZONE_DEVICE mapped pages. These pages are never > @@ -572,13 +572,19 @@ static void *grab_mapping_entry(struct xa_state *xas, > * establishment of new mappings in this address_space. I.e. it expects > * to be able to run unmap_mapping_range() and subsequently not race > * mapping_mapped() becoming true. > + * > + * Partial pages are included. If 'end' is LLONG_MAX, pages in the range > + * from 'start' to end of the file are inluded. > */ > -struct page *dax_layout_busy_page(struct address_space *mapping) > +struct page *dax_layout_busy_page_range(struct address_space *mapping, > + loff_t start, loff_t end) > { > - XA_STATE(xas, &mapping->i_pages, 0); > void *entry; > unsigned int scanned = 0; > struct page *page = NULL; > + pgoff_t start_idx = start >> PAGE_SHIFT; > + pgoff_t end_idx; > + XA_STATE(xas, &mapping->i_pages, start_idx); > > /* > * In the 'limited' case get_user_pages() for dax is disabled. > @@ -589,6 +595,11 @@ struct page *dax_layout_busy_page(struct address_space *mapping) > if (!dax_mapping(mapping) || !mapping_mapped(mapping)) > return NULL; > > + /* If end == LLONG_MAX, all pages from start to till end of file */ > + if (end == LLONG_MAX) > + end_idx = ULONG_MAX; > + else > + end_idx = end >> PAGE_SHIFT; > /* > * If we race get_user_pages_fast() here either we'll see the > * elevated page count in the iteration and wait, or > @@ -596,15 +607,15 @@ struct page *dax_layout_busy_page(struct address_space *mapping) > * against is no longer mapped in the page tables and bail to the > * get_user_pages() slow path. The slow path is protected by > * pte_lock() and pmd_lock(). New references are not taken without > - * holding those locks, and unmap_mapping_range() will not zero the > + * holding those locks, and unmap_mapping_pages() will not zero the > * pte or pmd without holding the respective lock, so we are > * guaranteed to either see new references or prevent new > * references from being established. > */ > - unmap_mapping_range(mapping, 0, 0, 0); > + unmap_mapping_pages(mapping, start_idx, end_idx - start_idx + 1, 0); > > xas_lock_irq(&xas); > - xas_for_each(&xas, entry, ULONG_MAX) { > + xas_for_each(&xas, entry, end_idx) { > if (WARN_ON_ONCE(!xa_is_value(entry))) > continue; > if (unlikely(dax_is_locked(entry))) > @@ -625,6 +636,12 @@ struct page *dax_layout_busy_page(struct address_space *mapping) > xas_unlock_irq(&xas); > return page; > } > +EXPORT_SYMBOL_GPL(dax_layout_busy_page_range); > + > +struct page *dax_layout_busy_page(struct address_space *mapping) > +{ > + return dax_layout_busy_page_range(mapping, 0, LLONG_MAX); > +} > EXPORT_SYMBOL_GPL(dax_layout_busy_page); > > static int __dax_invalidate_entry(struct address_space *mapping, > diff --git a/include/linux/dax.h b/include/linux/dax.h > index 6904d4e0b2e0..9016929db4c6 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -141,6 +141,7 @@ int dax_writeback_mapping_range(struct address_space *mapping, > struct dax_device *dax_dev, struct writeback_control *wbc); > > struct page *dax_layout_busy_page(struct address_space *mapping); > +struct page *dax_layout_busy_page_range(struct address_space *mapping, loff_t start, loff_t end); > dax_entry_t dax_lock_page(struct page *page); > void dax_unlock_page(struct page *page, dax_entry_t cookie); > #else > @@ -171,6 +172,11 @@ static inline struct page *dax_layout_busy_page(struct address_space *mapping) > return NULL; > } > > +static inline struct page *dax_layout_busy_page_range(struct address_space *mapping, pgoff_t start, pgoff_t nr_pages) > +{ > + return NULL; > +} > + > static inline int dax_writeback_mapping_range(struct address_space *mapping, > struct dax_device *dax_dev, struct writeback_control *wbc) > { > -- > 2.25.4 > -- Jan Kara SUSE Labs, CR _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org